کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
7056997 | 1458067 | 2014 | 18 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Results for high heat-flux flow realizations in innovative operations of milli-meter scale condensers and boilers
ترجمه فارسی عنوان
نتایج حاصل از اجرای حرارتی جریان گرما در عملیات نوآورانه خازن ها و دیگهای مقیاس میلی متر
دانلود مقاله + سفارش ترجمه
دانلود مقاله ISI انگلیسی
رایگان برای ایرانیان
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
جریان سیال و فرایندهای انتقال
چکیده انگلیسی
Innovative realizations of shear-driven boiling and condensing flows have been investigated within horizontal channels (with condensation or boiling on the bottom, horizontal surface). Results from boiling and condensing flows of FC-72 fluid in horizontal rectangular cross-section (2 or 6Â mm gap height and 15 or 24Â mm width, respectively) ducts of 1Â m length are presented. Utilizing a controlled presence of pulsatile mass flow rates, significant enhancements in heat-transfer rates are obtained for these innovative devices at a location within the device length - these enhancements (relative to non-pulsatile conditions) are sometimes >860% for condensing flows and >190% for boiling flows. The paper reports representative time-varying heat-flux values at this location in support of the understanding that this phenomena can potentially be used (in future experiments) to significantly enhance average heat-flux value over the entire length of an innovative boiler/condenser. The reported phenomena arises from superposing relatively fast time-scale (2.5-30Â Hz) flow rate pulsations on otherwise steady-in-the-mean flows to beneficially change certain flow variable averages - over the longer time-scale (<0.01Â Hz) of practical interest - relative to their values obtained in the absence of externally imposed pulsations. Such externally imposed pulsations may cause standing waves to form on the thin film interface. The observed asymmetric reduction in the mean film thickness (associated with high heat-flux values) is likely due to “stickiness” of wave-troughs resulting from interaction of phenomena associated with several length scales (namely nano-scale, micro-scale, and continuum length scales) and two different time scales - short (less than 0.5Â s) and long (greater than 1Â min). That is, associated micro-scale flows at wave-troughs interact with and, possibly, de-stabilize the local adsorbed layer (whose thickness may be <200Â nm and is exposed to phenomena such as disjoining pressures) on the wetting heat-exchange surface.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: International Journal of Heat and Mass Transfer - Volume 75, August 2014, Pages 381-398
Journal: International Journal of Heat and Mass Transfer - Volume 75, August 2014, Pages 381-398
نویسندگان
M.T. Kivisalu, P. Gorgitrattanagul, A. Narain,